1. Field of the Invention
The present invention relates to an image processing system for processing a digital image, such a system, e.g. comprising a scanner or a printer, and to an image processing method of processing digital images such as scanned images.
2. Description of Background Art
Image processing systems as known in the art are widely applied to produce high quality copies of scanned images. As such, an image processing apparatus may include a scanner such as a contact type scanner or a reduction type scanner for scanning an image thereby obtaining a digital representation of the image, i.e. a pixel-based representation of the scanned image, each pixel being described as a combination of RED (R), GREEN (G) and BLUE (B). Such a representation is also referred to as a representation in the RGB color space. Other color spaces such as CMYK are also known for representing the color associated with a pixel of a digitized image. In order to scan the image, an image processing apparatus may, e.g. comprise a charge coupled device (CCD), comprising a plurality of light-sensitive elements or photo-cells. Image processing apparatuses may further comprise a printing unit for providing a printed copy of the scanned image.
In general, an image processing system is further arranged to process the scanned image prior to the printing process. The purpose of such processing is to provide an image enhancement. The image processing system may also be arranged to convert a scanned image from one color space to another. Such a conversion may, e.g. be required when the color space of the scanning unit (e.g. RGB) is different from the available colors in the printing unit. Known processing steps as can be applied by such an image processing system, e.g. include background reduction or contrast enhancements.
The raw image as obtained from the scanner may comprise disturbances introduced during the scanning process. Such disturbances appear in the scanned image as (light) shaded areas on the background of the image. Such disturbances can, e.g. be caused by wrinkles or folds in the image being scanned. In particular, an image obtained from a contact-type scanner may suffer from the occurrence of such disturbances. In order to reduce disturbances occurring on the background of an image, different methods are known in the art. Reference can, e.g. be made to methods involving the determination of a dominant color in the image (or part of the image) and adjusting pixel values based on the dominant color. However, it has been observed that background reduction methods as known in the art not only result in the removal of unwanted shaded areas, they may also result in the removal of light shades that are wanted.